[Diy_efi] Can anyone diagnose this engine problem?

[Adam Wade]

--- joeld <joeld at ualberta.ca> wrote:

> What we've got:
> -polaris 600cc 2-stroke 2 cylinder snowmobile engine
> bottom end
> -our own billet cylinders and head
> -injectors in the cylinder walls
> -running a motec M4
> -centrifugal supercharger
> -45psi fuel pressure
> -88pound/hour injectors

> What its doing:
> It will rev up and idle perfect, right to 4500rpm or
> so and then it surges

The only thing that comes immediately to mind is that
you have an interference wave between the port timing
and the expansion chamber where the frequencies of
"resonance" vary by the period of your surging.  Have
you tried modifying the exhaust system?  With a
supercharger, there is little reason to run an
expansion chamber for exhaust scavenging and cylinder
filling, so you might try a straight pipe with a
silencer.  If you already have a straight pipe, try
lengthening it, perhaps a full foot to start to see
what effect changing the length would have.  Then tune
as necessary to keep your powerband nice and smooth.

=====
| 82 Honda CX500 Turbo (Cassandra)  90 Kwak Zephyr 550 (Daphne) |
| "It was like an emergency ward after a great catastrophe; it  |
|   didn't matter what race or class the victims belonged to.   |
|  They were all given the same miracle drug, which was coffee. |
|   The catastrophe in this case, of course, was that the sun   |
|     had come up again."                    -Kurt Vonnegut     |
| M/C Fuel Inj. Hndbk. @ Amazon.com -  http://tinyurl.com/6o3ze |


		
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